It is known to treat a uranium-containing oxide ore, such as pitchblende, by roasting the ore with 10% anhydrous metallic sulfide, such as FeS.sub.2 (pyrite), at gradually increasing temperature. Exemplary of this type of prior art is U.S. Pat. No. 3,152,862 to Fischer.
Furthermore, the use of ferric salts for extracting uranium from non-carbonaceous ores is known. Illustrative of this type of prior art are U.S. Pat. Nos. 2,570,120 to Handley et al, 2,736,634 to Gaudin et al, 2,737,438 to Gaudin, 2,847,275 to Yeager, and 2,894,804 to Sawyer et al. Sawyer et al use a ferric chloride leaching solution containing usually 2-15 pounds FeCl.sub.3.6H.sub.2 O per pound of uranium values to be recovered. Gaudin et al use a sulfuric acid leaching solution containing ferric ion, with ferric sulfate or ferric chloride being exemplary sources of the ferric ion. The leaching solution contains an amount of sulfuric acid (sp.gr.1.84) that is greater than or equal to the amount of ferric salt, on a weight basis. U.S. Pat. No. 2,890,933 to Michal et al views Gaudin et al as demonstrating that the presence of ferric ions in leaching solution increases substantially the proportion of uranium that can be leached from an ore (column 1, lines 45-49).
It is also known to recover uranium from carbonaceous materials, with U.S. Pat. Nos. 3,000,696 to Teichmann and 2,925,321 to Mariacher being exemplary of this type of prior art. The approaches in each of these patents requires an oxidation step whereby carbon is oxidized, prior to leaching to recover the uranium values. After the oxidation step, Mariacher roasts the uranium-containing ash with a sulfating agent such as pyrite, and the leaches the residue from the sulfating roast with fresh water, with an aqueous solution acidified with flue gas from the roasting step or with a dilute sulfuric acid.
This and the other prior art of which we are aware is deficient because in recovering uranium from carbonaceous ores, an oxidation step is required prior to any leaching step. This type of step is quite uneconomical from an energy standpoint and also from a time standpoint. Also, sintering often occurs during oxidation of the organic material and this produces a refractory residue. Additionally, much of the prior art uses a sulfuric acide leach solution. This approach results in excessive consumption of the acid and often large quantities of added oxidant are required. Other prior art uses a sodium carbonate leach solution. The difficulty with sodium carbonate is that solubilization of considerable organic material occurs, with a nearly impossible solid-liquid separation and excessive reagent consumption resulting.